User blog:Samuli.seppanen/New parts
It has been quite a while since I actually published pictures of new cheiroballistra parts, so here it goes. First the new little ladder forged from 6mm spring steel coupled with a better and stronger little arch forged from concrete reinforcement steel. Note how the tenons of the rungs simply project above the beams, instead of being riveted or otherwise attached to the beams. This allow one to bend the little ladder beams outwards when inserting their tenons into the pi-brackets in the field frame bars. As can be seen from the picture below, the little arch's retaining pins are significantly stronger (5mm) than the previous ones (3mm): Because the little ladder tenons are larger than previously, the wedge system needs to be adapted slightly. For testing purposes I hacked the thing together with three wedges: Here are close-ups of the little ladder tenons: The "feel" of the tenons changed dramatically when moving from 4mm to 6mm steel: the tenons now seem extremely robust and strong. The same goes for the rivet that goes through the wooden cross-piece: All in all, the whole little ladder / little arch / field frames package is extremely rigid now, so there should be no need to modify it further. I also decided to fix one long-time annoyance with the field frames: the pi-brackets are a bit flimsy, even though they seem to work ok. The current pi-brackets are made from 3mm steel and their ends are simply folded inside the field frame bars, which is not enough to prevent them from rotating a bit under load. So I bit the bullet and created a forging form and forged replacement pi-brackets from 5mm steel. Incidentally this also fits better with the manuscript ("They pittarions have width and thickness of the frame beams"): I ran out of time at the forge, so I have to hacksaw and file the tenons into the pi-brackets, instead of being able to use an angle grinder to save some time. That said, a hacksaw is definitely more accurate tool for the job. A "period" method would have been to flatten the ends in a swage, which I did not have, and did not feel the need to make. If I were to make more pi-brackets, I would definitely experiment with swaging. I also created two new proof of concept handles: The rectangular handle looks almost identical to the ones in manuscript diagrams. The idea is to lock the hollow part to a pair of locking pins attached to the case, or to a slot cut into the female dovetail. In either case a wooden dowel can be inserted through the hollow part to assist pullback. After locking the slider in place the dowel is removed. This increases safety: if the handle slips out of the retaining pin the worst that can happen is that the whole slider speeds forward and takes the cones with it. A wide, static handle could break one's next, or the whole torsion spring assembly could crash into one's face - or a combination of both. In addition in my earlier tests a wide pulling handle made operating the cheiroballistra quite difficult, as the handle was always in the way. Pictures of the finished composite slider and the new fork and tenon will follow later. Category:Blog posts Category:Backup Category:Cheiroballistra